package com.atguigu.rw;

import java.util.HashMap;
import java.util.Map;
import java.util.concurrent.locks.ReadWriteLock;
import java.util.concurrent.locks.ReentrantReadWriteLock;

/**
 * 独占锁（写锁） 异常只能被一个线程占有
 * 共享锁（读锁） 多个线程可以同时占有
 *
 * @author sx
 * @date 2022-02-19 16:16
 */
public class ReadWriteLockTest {
    public static void main(String[] args) {
        MyCacheLock myCacheLock = new MyCacheLock();

        //写入
        for (int i = 1; i <= 6; i++) {
            final int temp = i;
            new Thread(() -> {
                myCacheLock.write(temp + "", temp + "");
            }, String.valueOf(i)).start();
        }
        //读取
        for (int i = 1; i <= 6; i++) {
            final int temp = i;
            new Thread(() -> {
                myCacheLock.read(temp + "", temp + "");
            }, String.valueOf(i)).start();
        }
    }
}

class MyCacheLock {
    private volatile Map<String, Object> map = new HashMap<>();

    //读写锁，更加 细粒度的控制
    private ReadWriteLock readWriteLock = new ReentrantReadWriteLock();
//    private Lock lock = new ReentrantLock();

    //存，写入的时候，只希望同时只有一个线程写
    public void write(String key, Object value) {
        readWriteLock.writeLock().lock();
        try {
            System.out.println(Thread.currentThread().getName() + " 写入" + key);
            map.put(key, value);
            System.out.println(Thread.currentThread().getName() + " 写入OK");
        } catch (Exception e) {
            e.printStackTrace();
        } finally {
            readWriteLock.writeLock().unlock();
        }
    }

    //取，读取的时候，多个线程可以同时占有
    public void read(String key, Object value) {
        readWriteLock.readLock().lock();
        try {
            System.out.println(Thread.currentThread().getName() + " 读取" + key);
            Object o = map.get(key);
            System.out.println(Thread.currentThread().getName() + " 读取OK" + key);
        } catch (Exception e) {
            e.printStackTrace();
        } finally {
            readWriteLock.readLock().unlock();
        }
    }

}
